FIGS. 1-3 illustrate the typical way strings are run into a wellbore and secured to each other. FIG. 1 illustrates an upper wellbore 10 that has a tubular string such as casing 12 that is sealed in the wellbore with cement 14. A hanger/seal is illustrated generically as 16 since there may be situations with higher strings in the wellbore 10 that are above casing 12 or the casing 12 may be supported from a wellhead that is not shown. A subsequent tubular string 18 is assembled at the well surface and then further advanced into the lower wellbore 20 such that the upper end 22 overlaps with the lower end 24 of the casing 12. A running string 26 is releasably secured to the string 18 and the release occurs after a hanger/seal 28 is deployed to secure the string 18 to the casing 12. The running string is then pulled from the upper wellbore 10 as shown in FIG. 3.
The process described above requires time to assemble the string 26 to the length that string 18 will overlap at its upper end 22 with the lower end 24 of casing 12. Having secured the string 18 to the casing 12 the running sting then has to be raised and disassembled and racked near the rig at the surface. The assembly and disassembly time for the running string is the time that is desired to be saved with the present invention.
The method entails dropping a string into a wellbore through an existing string and controlling its speed in a variety of ways. Upon reaching the desired location the strings are secured to each other in a variety of ways for conducting further downhole completion or production operations. The time saved is the time normally used to assemble and pull the running string. Typically the weight of the string is used to advance it and a variety of speed control features can be used to regulate the rate of advance to the end destination which can be the hole bottom or at a desired level of overlap with the existing tubular to which the dropped string will be attached. A variety of attachment techniques are described.
In the past, braking systems have been designed to decelerate dropped objects so that they don't damage downhole components by striking them at high speeds. These devices are typically intended to make the falling object stop either as fast as possible or if there is interaction with a well feature then the intent is to stop the object as that feature is encountered before impact with a downhole tool such as a closed ball valve for example. Other designs expect impact and provide crushable leading ends to absorb the kinetic energy during rapid deceleration to minimize damage to downhole components. Some examples of the above are USP and Published Applications U.S. Pat. No. 7,779,907; 2010/0126732; U.S. Pat. Nos. 7,178,600; 7,328,748; 5,366,013; 6,109,355; 6,454,012; 7,451,809; 4,693,317; 5,083,623; 5,183,113; 5,875,875; 6,708,761; 6,817,598; 4,223,746; 4,658,902; 4,932,471; 4,679,669; 5,549,156; 5,590,714 and 7,296,638.
The present invention seeks to rapidly deploy a string as well as fixate the rapidly delivered string in a manner that will properly position the string to be secured and minimize pressure effects on the formation that can ensue from excessive string travel speed. Those skilled in the art will more readily appreciate the details of the preferred mode of the invention from the description below and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.